This circuit was found in a Popular Electronics from the 90s. It is based on components still common today and an optical coupler for the triac. The sensor is a thermistor.
We found this circuit in a 1980s documentation. The circuit uses general purpose transistors,...
This simple circuit for experimental LED sequencing is based on a multivibrator with transistors....
This circuit is from an American documentation from 1975. The circuit uses components of the time...